Pull Factors
Southern Europe, has some good places for other people to migrate to. Since many people from Europe left to go to the Americas, their languages have left an imprint in those countries. For example, a majority of South American countries speak Spanish, if the people were to migrate over to Europe the transition wouldn't be as hard as migrating to a country that speak a total different language. They also have started to provide care and jobs for women. That causes more women immigrants to want to go to Europe. Since the economy isn't that great, they have started to reconstruct it. When the immigrants come in, they take the less skilled jobs which is what helps the countries economically and financially. All of this has a positive effect for the economy and citizens.
Push Factors
Europe has had many of their local people leaving due to the large amount of unemployment and the government not doing anything to help. There's also a lot of overpopulation due to the amount of people migrating over, for example, the Syrian refugees have been coming over because of the war that has been going on. Because of that, the natives are starting to leave which caused the lack of people to work the jobs which effects the economy and government. There's also a lot of corruption in some countries like Spain and Greece.
There’s small amounts of people going into Europe from many different countries. When you add all of the numbers together, then you have a big number of immigrants.